Gastrointestinal (GI) symptoms are common in children with autism spectrum disorders (ASD). Recent studies report an increased frequency of GI symptoms in ASD children compared with typically developing children and those with other developmental delays (Valicenti-McDermott et al. (2006) J Dev Behav Pediatr 27(2 Suppl): S128-136; Ming et al. (2008) J Child Neurol 23: 6-13; Buie et al. (2010) Pediatrics 125 Suppl 1: S1-18; Bauman (2010) Neurotherapeutics 7(3): 320-327). Prospective, controlled studies suggest that as many as 70% of autistic children exhibit chronic GI-related symptoms (Valicenti-McDermott et al. (2006) J Dev Behav Pediatr 27(2 Suppl): S128-136; Horvath and Perman (2002) Current Opinion in Ped 14: 583-587; Levy (2007) Biol Psychiatry 61: 492-497) including diarrhea, laxative-dependent constipation, abdominal distension, failure to thrive, weight loss, feeding problems, and abdominal pain related to extreme irritability, aggression, and self-injury. These symptoms can be minimized or disappear following treatment of the underlying GI disorder (Jarocka-Cyrta et al. (2011) J Autism Dev Disord 41(3): 372-374). Retrospective chart review studies have shown no increase in GI symptoms in ASD children compared to neurotypical children (Black et al. (2002) BMJ 325(24): 419-421).
Gastrointestinal symptoms in children with autism spectrum disorder (ASD) are often associated with mucosal inflammatory infiltrates of the small and large intestine. Although distinct histologic and immunohistochemical properties of this inflammatory infiltrate have been previously described in this ASDIC group, molecular characterization of these lesions has not been reported. In ASD children with GI symptoms who undergo endoscopic and histologic examinations, inflammatory pathology is reported with high frequency (Horvath et al. (1999) J Pediatr 135: 559-563; Ashwood et al. (2004) J Clin Immunol 24: 664-673; Gonzalez et al. (2005) Arch Venez Pueric Pediat 69: 19-25; Krigsman et al. (2010) Autism Insights 1: 1-11). Features of the GI disease reported originally—ileocolonic lymphoid nodular hyperplasia (LNH) and ileocolitis—have since been expanded to include esophagitis (Horvath et al. (1999) J Pediatr 135: 559-563), atypical focal gastritis (Torrente et al. (2004) Am J Gastroenterol 4: 598-605), and enteritis (Torrente et al. (2004) Am J Gastroenterol 4: 598-60514; Torrente et al. (2002) Mol Psychiatry 7: 375-382; Balzola et al. (2005) Am J Gastroenterol 100: 979-981). Further analyses of the inflammatory infiltrate in the mucosa and the associated mucosal cytokine profiles have not only confirmed the presence of disease, but suggest characteristic features that distinguish the lesions in ASD children from the more well-described inflammatory bowel diseases (IBDs), i.e. Crohn's disease and ulcerative colitis (Ashwood et al. (2004) J Clin Immunol 24: 664-673; Torrente et al. (2004) Am J Gastroenterol 4: 598-605; Torrente et al. (2002) Mol Psychiatry 7: 375-382; Furlano et al. (2001) J Pediatr 38: 366-372). In parallel, disturbances in mucosal function (D'Eufemia et al. (1996) Acta Paediatr 85: 1076-1079; De Magistris et al. (2010) J Pediatr Gastroenterol Nutr 51: 418-424) and intestinal microflora (Finegold et al. (2002) Clin Infect Dis 35(Suppl 1): S6-S16; Williams et al. (2011) PLoS One 6(9): e24585) have been reported and may contribute to the GI pathology in ASD. A recent consensus report regarding GI disorders in individuals with ASDs concluded that ASD children with classic gastrointestinal symptoms often have a chronic inflammatory process “characterized by nodular lymphoid hyperplasia (NLH), enterocolitis, and mucosal infiltration by immune cells along the length of the gastrointestinal tract” (Buie et al. (2010) Pediatrics 125 Suppl 1: S1-18). While the clinical significance of these findings is still under investigation, it appears that the immunologic and inflammatory activity in the bowel may be part of a larger, systemic multi-organ immunopathology (Jyonouchi et al. (2001) J Neuroimmunol 120(1-2): 170-179; Jyonouchi et al. (2005) Neuropsychobiology 51(2): 77-85; Vargas et al. (2005) Ann Neurol 57(1): 67-81. Erratum in: Ann Neurol. 2005; 57(2): 304).
Currently, it is not clear whether the mucosal inflammatory changes seen in ASDIC children represent a milder variant of inflammatory bowel disease or whether a novel pathogenic process is underway. It is possible that a thorough molecular characterization of inflamed gastrointestinal tissue from ASD children and children with established IBD will help to answer this question. Several studies have described the use of gene expression profiling of biopsy-derived gastrointestinal tissue to provide molecular signatures for, and to distinguish between, Crohn's disease and ulcerative colitis (e.g., Wu et al. (2007) Inflamm Bowel Dis 13(7): 807-821; Galamb et al. (2006) World J Gastroenterol 12(43): 6998-7006; Costello et al. (2005) PLoS Med 2(8): e199; Lawrance et al. (2001) Hum Mol Genet 10(5): 445-456). Using this approach, one group identified a biomarker panel that could be used to distinguish IBD (Crohn's disease (CD) and ulcerative colitis (UC)) from “non-IBD” (in this case irritable bowel syndrome; IBS). The study further identified a subset of transcripts, consisting of seven genes, whose differential expression was useful in distinguishing the IBD subtypes, Crohn's disease and ulcerative colitis, with a high degree of sensitivity and specificity (von Stein et al. (2008) Gastroenterology 134(7): 1869-1881). Gene expression analysis has been recently utilized in the investigation of gastrointestinal dysfunction in ASD children. Building upon prior findings of mucosal brush border enzyme deficiencies in GI symptomatic ASD children, transcript levels of ileal disaccharidases were measured and found to be deficient in those patients (Williams et al. (2011) PLoS One 6(9): e24585. Epub 2011 Sep. 16). Using pyrosequencing analysis of mucoepithelial bacteria, a significant multi-component dysbiosis in the same ASD cohort was also reported.
Despite the published evidence (Horvath et al. (1999) J Pediatr 135: 559-563: Ashwood et al. (2004) J Clin Immunol 24: 664-673: Gonzalez et al. (2005) Arch Venez Pueric Pediat 69: 19-25: Krigsman et al. (2010) Autism Insights 1: 1-11: Torrente et al. (2004) Am J Gastroenterol 4: 598-605: Torrente et al. (2002) Mol Psychiatry 7: 375-382: Furlano et al. (2001) J Pediatr 38: 366-372), the debate still continues (Buie et al. (2010) Pediatrics 125 Suppl 1: S1-18; Galiatsatos et al. (2009) Can J Gastroenterol 23: 95-98: Wright (2010) BMJ 340: c1807) as to whether children with ASD and GI symptoms and non-specific mucosal infiltrates have conventionally recognized forms of IBD, a novel IBD phenotype, or no disease at all.
Detailed molecular information, generated from clinical specimens derived from ASDIC children, has the potential to provide valuable clarification of some of these issues. At a minimum, the analysis of differential gene expression in relevant tissue from this group of affected children will lead to a better understanding of the molecular processes involved in their inflammatory disease, including pathways that have been significantly impacted. This in turn may provide a more detailed understanding of the biology that underlies this condition.
Therefore, there is a need in the art for a molecular characterization of children with ASD and GI symptoms and for methods of diagnosing ASD, and GI disorders in children with ASD. The present invention satisfies this unmet need.